This invention relates to air conditioning wherein the intake of outside air is dehumidified. Heretofore, the desiccants employed have been expensive and because of their corrosive nature the dehumidifying section of air conditioning equipment has been fabricated of exceedingly expensive corrosive resistant materials, for examples calcium chloride or lithium chloride desiccants employing copper-nickel steel equipment is the usual requirement. Accordingly, it is a primary object of this invention to provide a relatively inexpensive and less corrosive desiccant, and a desiccant that is economically effective and which is adapted to use in relatively inexpensive equipment made of commercial grade materials such as steel that is protectively coated as by a paint or sealant, plating, or galvanizing and the like. It is cost effective dehumidification which is an object of this invention, all of which is accomplished without change to the downstream refrigeration and/or heating equipment.
There are a number of materials known to be useful as desiccants and particularly polymers proposed to be used as solids adapted to absorb water and to be regenerated as by drying for repeated use. However, the use of solid desiccant involves equipment implementation that can become bulky and oversized due to the nature of volume increase by the cube of the structural dimensions. With solid polymer the composition of the desiccant in a substrate is fixed. Therefore, the water uptake is dependent only upon temperature. However, with an aqueous polymer solution the liquid concentration can be variable, so that the water uptake is controllable, since the vapor pressure, concentration and temperature are all adjustable so as to maximize their functions. It is therefore an object of this invention to avoid objectionable size increase in the equipment by employing liquid polymers which avoid the same as capacity requirements increase, since they are fluid and are therefore more versatile in their applications. Such polymers which are feasible to be used as packed desiccants are:
Polystyrene sulfonic acid sodium salt PA0 Polyacrylic acid ammonium salt PA0 Poly (methacrylic acid) sodium salt PA0 Poly (n-vinylacetamide vinyl sulfonate) sodium salt PA0 Polyacrylic acid sodium salt PA0 Cellulose sulfonate sodium salt PA0 Methyl cellulose
However, it is a liquid desiccant of polymer material with which this invention is concerned, and to this end it is an object to provide the same in the form of hygroscopic fluids as a desiccant, rather than in the form of solid salts.
Water vapor sorption by polymers is a recognized advantage, however there is criticality involved in the salt to be employed therewith, the water uptake capability being most important. The ion-dipole interaction is therefore to be considered, reference being made to FIGS. 3a, 3b and 3c of the drawings, which illustrate the comparisons between the use of Lithium, Sodium and Potassium. It becomes apparent that the Lithium ion Li+ accomodates a far greater amount of water, of the three, due to to its small cationic size as compared with either Sodium Na+ or Potassium K+. The atomic weight and corresponding cationic size of various elements are considered, as follows:
______________________________________ Li Lithium 6.9 Na Sodium 23 K Potassium 39 Ca Calcium 40 Ca Cesium 133 ______________________________________
Therefore, it is an object of this invention to employ any one of the known salts in the sulfonation of the aforementioned polymers to be employed in a liquid form as a hygroscopic liquid, especially as a desiccant. Accordingly, Polystyrene Sulfonic Acid Lithium Salt Solution or PSSALS is a preferred embodiment herein (see FIG. 5b).
It is an object of this invention to implement the advantages of a polymer-salt solution in dehumidification equipment, as a low cost unit or section of equipment applicable to existant refrigeration air conditioning equipment, without major change thereto. Air conditioning involves generally, an outside air supply, a supply air discharge into a building interior, return air intake from the building interior, and a relief air discharge. The polymer-salt solution dehumidifier of the present invention is adapted to the outside air intake and to the relief air discharge of the existent air conditioning equipment. It is an object of this invention to advantageously employ the outside supply air intake temperature for desiccant treatment. It is also an object of this invention to advantageously employ a heat-pipe to extract heat after dehumidification and to dissipate that heat. The air dehumidifier intake section herein disclosed replaces an air intake or power section of usual equipment and is preferably attached to a blower section unit that separates the relief air from the return air, as shown.
An air conditioning system involves the discharge of relief air that is replaced by outside supply air. The volume ratio of these two columns of air varies as a result of variations in leakage from the conditioned air space involved, the relief air being stale interior air retrieved at a place or places of higher interior temperature and where stale air exists. Consequently, relief air is substantially warmer than supply air (the conditioned air), it being an object of this invention to advantageously employ warmer relief air before its discharge as exhaust air, by dissipating its usable heat energy through the regenerater section of the dehumidifier. It is still another object of this invention to advantageously employ the heat energy rejected by the heat pipe, or pipes, for this purpose, as disclosed in each of the embodiments of this invention as later described.
In a second embodiment of this invention, FIG. 4, the adsorption element of the dehumidifier is a heat exchanger over which the polymer-salt solution is wetted and through which a coolant is circulated for reduced temperature intake air into the air conditioning equipment. In practice, the coolant is controlled and circulated by a pump, over or through a heat exchanger, and chilled or cooled as by means of an evaporative cooling tower (employing water). The heat-pipe relationship remains the same as in the first embodiment.
In a third embodiment of this invention, FIG. 6, the adsorption element of the dehumidifier is the absorber section or hot end of the heat-pipe and over which the polymer-salt solution is wetted for water vapor sorption and through which the heat-pipe refrigerant recirculates for heat absorption. There is a simultaneous heating effect and cooling effect on the outside supply air, said air being heated as a result of the water vapor sorption by the polymer-salt solution while being cooled as a result of heat adsorption by the hot end of the heat-pipe. It is to be understood that the use of a hygroscopic desiccant liquid involves regeneration through the application of heat, which is shown herein generally as a supplemental heat source, all according with state of the art processes. In accordance with this invention, regeneration is by means in the discharge of relief air over the heat rejector section or cold end of the heat-pipe.
In a fourth embodiment of this invention, FIG. 9, a central regenerater unit services a multiplicity of dehumidifier contactor sections. That is, a multiplicity of dehumidifier means, each serving an independent air conditioning unit, commingles weakened desiccant to be strengthened by a single regenerater section or unit. This combination reduces the complexity of the dehumidifier means operable with each air conditioner unit, and makes possible the use of a larger most efficient regenerater unit for cost efficient operation.
In a fifth embodiment of this invention, FIG. 10, the regenerater section is a self contained and self operable unit wherein heat is the prime mover directly applied to the water saturated desiccant without resort to contact with blower motivated air. Reference is made to the polymer-salt desiccant solution disclosed herein as the preferred hygroscopic liquid for the adsorption of water vapor. This preferred desiccant is known to be more viscous than the usual prior art desiccant such as Lithium Chloride, and though spray bar distribution is practical in the contacter section of a dehumidifier means, regeneration by means of spray bar and interface heat application presents liquid handling problems, because of the higher viscosity. It is an object of this invention, therefore, to directly process the weakened higher viscosity desiccant through a multi effect boiler concentrater, using the direct application of heat in a first high pressure stage followed by at least one or more lower pressure stages and with a counter flow of desiccant from which water vapor is driven out of the weakened water saturated liquid and returned to the contacter section or sections as strengthened desiccant.